MESODON. 321 



The specimens figured show how variable the species is in size. In color it 

 is also very variable ; sometimes it is found of a uniform red, at others albino. 



The varieties mentioned by PfeifFer and Deshayes are distinguished merely 

 by the revolving bands. In a large suite of specimens it is rare to find two on 

 which these bands and lines are similarly arranged. Some have a parietal tooth. 



It would appear from the statement made by Dr. Kirtland that it? habits are 

 somewhat peculiar. " Wet marshes are its principal resort, where, during 

 summer, it may be seen climbing about on weeds and blades of grass, appar- 

 ently endeavoring to avoid the water collected beneath it. At the approach 

 of winter it retreats to the tops of the carex-bogs, where several dozen may be 

 found collected together in a torpid state, with the mouths of their shells closed 

 with an epiphragm. They usually form a shallow excavation on the bog, con- 

 cealed beneath the tufts of dead grass." The numbers collected in these 

 retreats are sometimes " agglutinated into one mass." This habit of attaching 

 themselves to each other in numbers, during their hibernation, I have not wit- 

 nessed in any other of our species, but I believe it is common in some European 

 species. 



Jaw arcuate, of uniform width ; ends blunt ; anterior surface with numerous, 

 crowded ribs, denticulating either margin. 



Lingual membrane (PL VIII. Fig. L) with 42 1 42 teeth; 17 perfect 

 laterals. 



Genitalia (see Vol. I., 1. c.). Penis sac long, stout, with a very highly devel- 

 oped prepuce on the greater part of its course, then tapering to its summit, 

 where it receives the vas deferens and retractor muscle ; genital bladder long, 

 subcylindrical, its duct but slightly smaller, short, swollen at its entrance into 

 the vagina ; oviduct greatly convoluted. 



Mesodon Fennsylvanica, GREEN. 

 Vol. III. PI. VII. 



Shell imperforate, convex, elevated ; epidermis yellowish horn-color, or rus- 

 set ; whorls 6, convex, with crowded, elevated, oblique stria? ; suture distinctly 

 marked ; aperture subtriangular, contracted by the peristome ; peristome white, 

 naiTow, reflected, not flattened, with sometimes a slight thickening on the inner 

 side near the base; umbilical region indented. Greater diameter 17, lesser 

 15 mill.; height, 11 mill. 



Helix Pennsylvanica, GREEN, Contributions to Macl. Lye., Nos. 1, 8. BINXEY, 

 Bost. Joum. Nat. Hist., I. 483, PI. XVI. (1837) ; Terr. Moll., II. 105, PI. 

 VII. PFEIFFER, Symboloe, II. 36 ; Mon. Hel. Viv., I. 291 (excl. H. clausa) ; 

 IV. 321 : in CHF.MNITZ, ed. 2, II. 51, t. LXXIII. Figs. 4, 5 (excl. H. clausa). 

 -DEK.VY, X. V. M..11., 41, PI. III. Fig. 35 (1843). MRS. GRAY, Fig. Moll. 

 An., PI. CCXCI. Fig. 5, from Bost. Journ., no descr. REEVE, Con. Icon., 

 No. 670 (excl. syn.). BLAND, Ann. N. Y. Lye., VI. 299 (1858). \V. G. 

 BINNEY, Terr. Moll., IV. 45 ; L. & Fr.-W. Sh., I. 140 (1869). 



VOL. IV. 21 



